In any number of commercial and other applications, such as agricultural, oil exploration, mining, geological, and infrastructure projects, archeological explorations, and so on, it would be useful, and in some cases essential, to be able to return to “exactly” the same position, e.g., within a predefined level of precision, such as 10 cm, 5 cm, or 2 cm, at times separated by multiple months, years or even decades, despite “continental drift,” sometimes called plate tectonics, which is the process by which a portion of Earth's upper surface moves over the mantle like a set of plates. When determining the position of a moveable object, even if a determined position has been determined with great accuracy (e.g., within a predefined level of precision, such as 10 cm, 5 cm, or 2 cm,) with respect to a virtual global reference frame (sometimes called a global coordinate system) using precise point positioning (PPP) or other absolute mode of navigation, the determined position is typically not a “repeatable position” over a long period of time (e.g., over a period of time exceeding a predefined amount of time, such as one year), because a moveable object at the same determined position, P1, determined at the current time, and determined again a year later, will be separated in fact by a distance D corresponding to a rate of tectonic plate movement and corresponding to the amount of time between the two times at which the position was determined.
Sixteen major plates have been identified, each moving at a different velocity (speed and direction). For example, the North American plate moves about 2 cm per year, while the Australian plate moves about 8 cm per year. FIG. 2 illustrates the major tectonic plates, also herein called tectonic terrestrial plates.
In navigation systems that use a differential mode of navigation, such as real-time kinematic (RTK) based systems, base station receivers (often called base stations), located at surveyed positions, periodically broadcast satellite data to moving object receivers. Moving object receivers compare their own phase measurements with the ones received from the base station, and use that information plus the position of the base station to determine their own position. Since each base station is positioned on a single tectonic plate, and its position is known, RTK-based navigation systems automatically adjust for continental drift. However, the use of differential modes of navigation is not practical in many settings, due to either the cost of such systems, or the lack of based stations positioned sufficiently close to the position(s) of the moveable objects whose position needs to be determined with high precision in real time.
Navigation systems using absolute modes of navigation typically use standard point positioning (SPP) or precise point positioning (PPP). In absolute mode navigation systems, a moveable object's coordinates are determined with respect to a virtual global reference frame. However, if “the ground underneath” a surveyed position moves, relative to the virtual global reference frame, between the time of a first survey and a second survey, when the moveable object returns to the exact same coordinates at the time of the second survey, it will not be at the same position on the ground. It would therefore be useful to have the navigation systems of moveable objects that require long term, high precision repeatability of surveyed positions to include mechanisms for automatically adjusting for tectonic plate movements.